This application claims the benefit of Danish Application No. PA 2003 01347 filed Sep. 17, 2003 and PCT/DK2004/000629 filed Sep. 17, 2004, which are hereby incorporated by reference in their entirety.
The present invention concerns a method to obtain weed control properties in joint filling sand through addition of slowly soluble natural minerals or environmentally acceptable industrial wastes.
Joint filling sands are generally used to finish and partly seal the surface of pavements, whether these are made of natural or industrially produced paving stones. The purpose of the joint filling sand is to fill the gaps in the joints, at the same time imparting sufficient load carrying strength to the finished surface, while maintaining its flexibility. As a recurred problem, joint filling sands in general use can also function as substrate for plant and fungus growth. Higher plants, algae and lichens are all strictly considered, weeds (=unwanted plant growth), except in some cases where mosses covering joints can be accepted in relatively old pavements with only moderate traffic, seemingly preventing (other) weeds from getting established. The term weed in this context covers any plant growth in joints. Plant growth in the joint filling causes not only impairment of the appearance of the pavement, but if unchecked can seriously damage the technical functioning of the pavement. Hence it is desirable to develop methods for effective control of weeds in joint filling sands.
To control or prevent weed growth in joint filling sands, commonly applied technologies rely on a multitude of different principles. These include the following control methods alone or in combination: Treatment of the affected area with sodium chloride or other readily soluble salt, treatment of the paved area with weed toxins, mechanical removal, scorching with a flame, electrical or microwave treatment, steaming or sealing the joint using various waxes, resins, or cements forming an impenetrable surface through which weeds cannot get established.
Electrical treatment or microwave treatment is very energy intensive (vide for example Patent application CA2299301) and/or are only effective when applied to seeds under germination. Apart from treatment with toxins, all of the other methods are labour intensive and some methods will to some degree impair the flexibility of the joints and must be repeated at short intervals to be effective. Toxin treatment, being most effective has the disadvantage of being potentially harmful to surrounding vegetation and most effective formulations have inherent acute and long term personnel safety problems and/or can cause pollution of the environment.